for (int c0 = 0; c0 <= 14; c0 += 1)
  for (int c1 = max(2 * c0 - 12, -c0 + 3 * ((c0 + 1) / 2)); c1 <= min(2 * c0, c0 / 2 + 9); c1 += 3)
    s0((2 * c0 - c1) / 3, (-c0 + 2 * c1) / 3);
